The invention relates to satellite payload processing systems and recovery of digital baseband signals from uplink transmissions.
There presently exists a population of over 4 billion people that are generally dissatisfied and underserved by the poor sound quality of short-wave radio broadcasts, or the coverage limitations of amplitude modulation (AM) band and frequency modulation (FM) band terrestrial radio broadcast systems. This population is primarily located in Africa, Central and South America, and Asia. A need therefore exists for a satellite-based direct radio broadcast system to transmit signals such as audio, data and images to low-cost consumer receivers.
A number of satellite communications networks have been developed for commercial and military applications. These satellite communications systems, however, have not addressed the need to provide multiple, independent broadcast service providers with flexible and economical access to a space segment, nor consumers"" need to receive high quality radio signals using low-cost consumer radio receiver units. A need therefore exists for providing service providers with direct access to a satellite and choices as to the amount of space segment that""s purchased and used. In addition, a need exists for a low-cost radio receiver unit capable of receiving time division multiplexed downlink bit stream.
In accordance with an aspect of the present invention, a satellite payload processing system for processing a single-channel-per-carrier, frequency division multiple access uplink signal is provided which comprises a polyphase demultiplexer processor for separating the uplink signal into a time division multiplexed data stream of symbols. The polyphase demultiplexer processor presents the symbols corresponding to each of a plurality of carriers at respective ones of the frequencies in the uplink signal sequentially to an output of said polyphase demultiplexer processor. A phase shift keying demodulator is connected to the output of the polyphase demultiplexer processor for demodulating the stream of symbols into corresponding time division multiplexed stream of digital baseband bits.